So the ISP sits in the loop and I know the old ones you need to have the mix level all the way up
But the new rectos have the "improved series loop" so does the mix level still need to be all the way up.
Thanks.
The new serial loop doesn't have a mix level, it's a volume control. Basically, you should leave it at 12:00 where the signal when you engage the loop is exactly as loud as with a bypassed loop (if not, you can adjust the volume here)